From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A5A83C433E6 for ; Thu, 28 Jan 2021 13:01:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5716664DDE for ; Thu, 28 Jan 2021 13:01:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231812AbhA1NBj (ORCPT ); Thu, 28 Jan 2021 08:01:39 -0500 Received: from www262.sakura.ne.jp ([202.181.97.72]:59640 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231717AbhA1NBe (ORCPT ); Thu, 28 Jan 2021 08:01:34 -0500 Received: from fsav102.sakura.ne.jp (fsav102.sakura.ne.jp [27.133.134.229]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 10SCxYc6075273; Thu, 28 Jan 2021 21:59:34 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav102.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav102.sakura.ne.jp); Thu, 28 Jan 2021 21:59:34 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav102.sakura.ne.jp) Received: from [192.168.1.9] (M106072142033.v4.enabler.ne.jp [106.72.142.33]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id 10SCxY3q075270 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NO); Thu, 28 Jan 2021 21:59:34 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: [PATCH v2] smackfs: restrict bytes count in smackfs write functions To: Sabyrzhan Tasbolatov Cc: andreyknvl@google.com, casey@schaufler-ca.com, jmorris@namei.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, mhocko@suse.com, serge@hallyn.com, syzbot+a71a442385a0b2815497@syzkaller.appspotmail.com References: <3c35f7cc-1c8d-2fa0-6bc9-bde4e96017ce@i-love.sakura.ne.jp> <20210128115801.1096425-1-snovitoll@gmail.com> From: Tetsuo Handa Message-ID: <5271074f-930a-46e9-8ece-2cc65d45dc19@i-love.sakura.ne.jp> Date: Thu, 28 Jan 2021 21:59:33 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: <20210128115801.1096425-1-snovitoll@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/01/28 20:58, Sabyrzhan Tasbolatov wrote: > @@ -2005,6 +2009,9 @@ static ssize_t smk_write_onlycap(struct file *file, const char __user *buf, > if (!smack_privileged(CAP_MAC_ADMIN)) > return -EPERM; > > + if (count > PAGE_SIZE) > + return -EINVAL; > + > data = memdup_user_nul(buf, count); > if (IS_ERR(data)) > return PTR_ERR(data); > @@ -2740,10 +2754,13 @@ static ssize_t smk_write_relabel_self(struct file *file, const char __user *buf, > return -EPERM; > > /* > + * No partial write. > * Enough data must be present. > */ > if (*ppos != 0) > return -EINVAL; > + if (count == 0 || count > PAGE_SIZE) > + return -EINVAL; > > data = memdup_user_nul(buf, count); > if (IS_ERR(data)) > Doesn't this change break legitimate requests like char buffer[20000]; memset(buffer, ' ', sizeof(buffer)); memcpy(buffer + sizeof(buffer) - 10, "foo", 3); write(fd, buffer, sizeof(buffer)); ?